It could also be the stress. When you stress a lot about something your period can be late.
The best thing you can do now if you dont get your period is to go back and take another pregnancy test. And then take it from there.
If youre not pregnant then there is nothing to worry about. Dont start freaking out now, nothing is sure yet. If you should be pregnant though, you are going to have to tell your mom sooner or later because she is going to find out. And she might actually be able to help you with your choice. Write her a letter if you are too scared to tell her.
But really I wouldnt start freaking out right now, I know its easier said than done, but wait for the result of the pregnancy test and tell the nurse exactly how much too late your period is.
Hope things go well for you.
PM me if you want to talk.
Take care xxx